1. Field of the Invention
This invention relates to cold flow improvers for use in middle distillate fuel oils and, more particularly, relates to cold flow improving oligomers of ester-containing halopolyalkylenes.
More particularly, the present invention relates to polymerizable ester-containing halopolyalkylenes obtained by replacing at least a portion of the halogens of the halopolyalkylenes with polymerizable ester groups, and to oligomers of such polymerizable ester-containing halopolyalkylenes.
In storage and use of heavy oils, such as lubricating oils, problems associated with cold flow have long been in existence and have been recognized in the art. Cold flow problems arise through the formation of solid or semi-solid waxy particles with an oil composition. For example, in the storage of furnace oils or diesel oils during the winter months, temperatures may decrease to a point as low as -26.degree. C. to -40.degree. C. The decreased temperatures often cause crystallization and solidification of wax in the distillate fuel oil.
Cold flow properties of an oil can be categorized as either pour-point properties or operability properties. The pour-point of an oil is defined as the lowest temperature at which the oil will pour or flow when chilled under specific conditions. The pour-point is reduced by reducing the amount of crystallization that occurs. The operability of an oil is defined as the temperature at which an oil will pass through a standardized filter in a set period of time. Thus, the operability of an oil can be improved by reducing the size of the crystals. Pour-point and operability problems also exist in the storage and use of distillate fuel oils, particularly at low temperatures.
2. Description of Prior Art
Chlorinated polyethylenes, ethylene-vinyl ester-type copolymers and ester-containing halopolyalkylenes have been employed as cold flow improvers for hydrocarbon fuels.
The following patent illustrates chlorinated polyethylenes used to improve cold flow:
U.S. Pat. No. 3,337,313 PA1 U.S. Pat. No. 3,048,479 PA1 U.S. Pat. No. 3,093,623 PA1 U.S. Pat. No. 3,131,168 PA1 U.S. Pat. No. 4,568,726 PA1 U.S. Pat. No. 4,568,359 PA1 U.S. Pat. No. 4,554,327 PA1 U.S. Pat. No. 4,553,980 PA1 U.S. Pat. No. 4,544,712 PA1 U.S. Pat. No. 4,541,839 PA1 U.S. Pat. No. 4,536,191 PA1 U.S. Pat. No. 4,536,551
The following patents illustrate ethylene-vinyl ester-type copolymers used to improve cold flow:
Often both types do not exhibit equal cold flow improving activity in the same fuel. One type may be effective in one type of fuel while the other may be effective in another type of fuel.
The following patents illustrate ester-containing halopolyalkylenes used to improve cold flow:
It has now been discovered that ester-containing halopolyalkylenes can be oligomerized to produce cold flow improvers which are more effective than known ester-containing halopolyalkylenes and which are unexpectedly more effective than an equivalent amount of the corresponding single-unit ester-containing halopolyalkylenes.